ARC Centre of Excellence for Core to Crust Fluid Systems
These balls and dendrites of native vanadium are enclosed in crystals of hibonite (CaAl12O19) ejected from Cretaceous volcanoes on Mt Carmel in northern Israel. The balls nucleated as droplets on the faces of growing hibonite crystals, when a vanadium melt became immiscible with the Ca-Al silicate melt that was crystallising hibonite, grossite (CaAl4O7) and spinel, in a magma chamber near the crust-mantle boundary. The dendrites grew out into the silicate melt, and were overgrown by the hibonite. The presence of vanadium melts testifies to the most reduced conditions yet recognised on Earth, equivalent to the oxygen fugacity of the early solar nebula, where the atmosphere was dominated by hydrogen. See Research highlight.